1. Field of the Invention
The present invention relates to a magnetic recording and/or reproducing apparatus and a recording medium thereof in which the recording track pattern is physically formed in advance.
2. Description of the Prior Art
A magnetic recording and/or reproducing apparatus and a recording medium in which a recording track pattern is formed during manufacture of the recording medium have been proposed so far. FIG. 1 schematically illustrates a recording medium (magnetic disc) on which a recording track pattern is pre-formed. In FIG. 1, reference numeral 50 depicts the entirety of a magnetic disc. The magnetic disc 50 has formed at its center an aperture 51 into which a spindle (not shown) is inserted, and recording tracks 52 made of a magnetic material are concentrically formed around the aperture 51. A connection pattern 53 also is provided to make the respective recording tracks 52 equal in electrostatis potential. When the above-mentioned magnetic disc 50 is produced, a magnetic material having conductivity is deposited on the whole upper surface of a disc-shaped glass plate 54 in a layer fashion by a sputtering-process and then a necessary recording track pattern is formed on the magnetic disc 50 by some suitable process such as an etching-process or the like.
For the magnetic disc 50 thus arranged, the recording track 52 is recorded and/or reproduced and the tracking also is performed as follows.
FIG. 2 shows a perspective view of an example of a recording and reproducing head. In FIG. 2, reference numeral 60 generally depicts a recording and reproducing head. The recording and reproducing head 60 iS composed of a magnetic head 61 of a single pole for effecting the vertical magnetization and a slider portion 62 which serves also as a feedback portion of a magnetic line of force. On the lower surface of the slider portion 62, there are formed predetermined grooves which are used to float the entirety of the recording and reproducing head 60 from the magnetic disc 50 by effectively utilizing an air film. Electrodes 63a and 63b for generating electrostatic capacity between them and the magnetic material forming the recording track 52 are provided on the lower surface of the slider portion 62 at the positions opposing the respective sides of the recording track 52 when the magnetic head 61 is opposed to the recording track 52. By means of a supporting arm 64, the recording and reproducing head 60 is coupled to a head driving means which will be described later.
FIG. 3 shows partly in block form an example of an arrangement of a head driving circuit. Referring to FIG. 3, conductors led out from the above-mentioned electrodes 63a and 63b are both connected to an electrostatic capacity detector 71 which detects electrostatic capacities Ca and Cb corresponding with the areas in which the electrodes 63a and 63b are opposed to the magnetic material forming the recording tracks 52. These electrostatic capacities Ca and Cb are supplied to an adder 72 and a subtracter 73, from which there are derived an added value C+ and a subtracted value C-, respectively. Then, the added value C+ and the subtracted value C- are supplied to a divider 74 which derives a calculated value (C-/C+).
Track moving information from a central processing unit (CPU) or the like, not shown, is supplied to a control circuit 75 and the difference of an output signal from the control circuit 75 and the above-mentioned calculated value (C-/C+) is supplied from a subtracter 76 to a driver circuit 77. A driving signal from the driver circuit 77 is supplied to a head driving means 78 which is coupled to the recording and reproducing head 60 by means of the aforementioned supporting arm 64. The recording and reproducing head 60 is thereby moved along the recording tracks 52 on the basis of the control signal from the control circuit 75. Simultaneously, the tracking control is performed in a manner such that the areas in which the respective electrodes 63a, 63b are opposed to the respective recording tracks 52 become equal. Accordingly, in this state, the center of the magnetic head 61 becomes aligned with the center of the recording track 52 and the recording track 52 is recorded and reproduced by the magnetic head 61 under this condition. During this tracking control, bad influences such as fluctuation of the floated amount of the recording and reproducing head 60 from the magnetic disc 50 and so on are eliminated because the added value C+ and the subtracted value C- are divided by the divider 74, and thus the tracking control can be carried out satisfactorily without such influences.
In the above-mentioned recording and reproducing apparatus, if a stray capacity is changed due to the drift of temperature, the vibration of interconnection or the like, then it cannot be determined whether or not such a change of stray capacity is caused by the position of the recording and reproducing head 60, resulting in a position detection error. That is, fluctuations occurred simultaneously in the two electrodes 63a, 63b such as their floating amount can be removed by the above-mentioned division. This division cannot eliminate the change of the stray capacity due to the drift of temperature, the vibration of interconnection and so on because they take place in each of the electrodes 63a, 63b independently.